1. Field of the Invention
The present invention relates generally to an optical pickup, and more particularly to an optical pickup and optical recording and reproducing apparatus using the same, which can promptly process optical disk information without increasing a rotation speed of an optical disk, and cope with various types of optical disk media using light beams with different wavelengths.
2. Description of the Related Art
Generally, an optical pickup is a device for reproducing signals recorded on various optical disks or recording signals on optical disks. Recently, an optical pickup having a large storage capacity and a high processing speed has been developed.
First, the development trend of the storage capacity of an optical pickup is described below.
Recently, Digital Versatile Disk (DVD) and Compact Disk (CD) products have been generally used.
For example, CD products store information of 650 MB using a light beam with a wavelength of 780 nm, and DVD products store information of 4.7 GB using a light beam with a wavelength of 650 nm.
Meanwhile, with the beginning of High Definition (HD) broadcasting, Blu-ray products capable of sufficiently storing various information have been developed.
The Blu-ray products are planned to increase the information storage capacity to store information with a capacity equal to or greater than 25 GB using a light beam with a wavelength of 405 nm.
As described above, an optical pickup recording manner has been rapidly developed.
That is, a smaller beam spot can be formed using a short wavelength light beam, and higher information recording density can be realized using the smaller beam spot.
However, since the development speed of the recording manner is higher than the expansion speed of markets, a great number of consumers desire products in which both a large capacity recording medium and an inexpensive recording medium with small capacity can be compatibly used.
However, optical pickups marketed until now are problematic in that, since they cannot fully cope with various types of optical recording media, such as CD products, DVD products and Blu-ray products, the optical pickups do not satisfy to consumers.
Next, the development trend of the information processing speed of optical pickups is described below.
Recently, products which increase an information processing speed by increasing the rotation speed of an optical disk have been marketed. However, these products have disadvantages due to the increase of the rotation speed.
For example, if the rotation speed of an optical disk increases, very high flatness is required in the optical disk to correct the focus of light beams, thus increasing the cost of the optical disk due to the requirement.
Therefore, an optical pickup constructed to increase an information processing speed using multiple beams without increasing the rotation speed of an optical disk is disclosed in U.S. Pat. No. 6,385,143.
FIG. 1 is a view showing the construction of the optical pickup of the U.S. Pat. No. 6,385,143.
An operation of the optical pickup is described with reference to FIG. 1. A light beam 3 generated by a laser diode 4 is divided into multiple beams 3-1, 3-2, 3-3, 3-4 and 3-5 by a grating 5. The multiple beams pass through a beam splitter 6 and are converted into parallel beams by a collimator lens 7, and the parallel beams are focused on an optical disk 1 by an objective lens 8.
Beams reflected from respective tracks are converted into parallel beams by the objective lens 8 and are focused on a photo detector 2 (photo diode array) by the collimator lens 7. At this time, since the beam splitter 6 is disposed between the photo detector 2 and the collimator lens 7, focused beams propagate toward the photo detector 2 without returning to the grating 5.
Multiple beams, diffracted and generated by the grating 5, correspond to respective tracks, and a light beam reflected from each of the tracks corresponds to a cell of the photo detector 2. Therefore, pieces of track information corresponding to the respective beams are transmitted to the corresponding cells of the photo detector 2, and converted into electrical signals by the photo detector 2.
Due to this construction, the optical pickup can promptly process optical disk information using multiple beams without increasing the rotation speed of the optical disk.
However, the conventional optical pickup is problematic in that, since it employs a fixing diffraction grating allowing only light of a specific wavelength, the optical pickup cannot cope with various optical disk media using light beams with different wavelengths.